Actually this is all coming back to me now. I tried this when event input first came out and had the same problem with large numbers of event inputs. The only alternative is using midi over lan and external midi in VSL EP. The latency is horrible but you can insert a midi track plugin in DP called time shift and offset everything early by the same number of samples as the latency. Not perfect but it works. The logic environment layer solution apparently works really well and Cubase uses vst3 so doesn't have the problem so its just Pro Tools and us DP people out here!
We need VST3 support in DP then we'd be sorted.